Implement client event_hooks flow

[cnpryer]

No description provided.

[github-actions]

Benchmark Results

Commit: a4f5593

get  (n=5000)
  package      mean   median    stdev      min      max  (ms)    ratio
  --------------------------------------------------------------------
  httprs      0.290    0.288    0.023    0.245    0.785
  httpx       0.803    0.768    0.199    0.657   11.876    2.77x slower
  requests    0.886    0.852    0.163    0.773    8.505    3.05x slower

post_bytes  (n=5000)
  package      mean   median    stdev      min      max  (ms)    ratio
  --------------------------------------------------------------------
  httprs      0.402    0.412    0.040    0.330    0.820
  httpx       0.891    0.845    0.102    0.747    1.414    2.22x slower
  requests    1.062    1.005    0.122    0.889    3.827    2.64x slower

post_json  (n=5000)
  package      mean   median    stdev      min      max  (ms)    ratio
  --------------------------------------------------------------------
  httprs      0.818    0.810    0.082    0.729    2.483
  httpx       1.222    1.174    0.105    1.067    1.698    1.49x slower
  requests    1.307    1.249    0.114    1.130    1.911    1.60x slower

post_form  (n=5000)
  package      mean   median    stdev      min      max  (ms)    ratio
  --------------------------------------------------------------------
  httprs      0.334    0.330    0.031    0.304    2.047
  httpx       1.035    0.988    0.109    0.885    2.002    3.10x slower
  requests    1.141    1.091    0.147    1.004    3.598    3.42x slower

[github-actions]

Ecosystem Tests

Commit: a4f5593

repo	baseline package	baseline passed	compat passed	accepted regressions	remaining real regressions	total score
openai/openai-python	httpx	559	462	96 (17.2%)	1 (0.2%)	558/559 (99.8%)
anthropics/anthropic-sdk-python	httpx	583	484	89 (15.3%)	10 (1.7%)	573/583 (98.3%)
python-telegram-bot/python-telegram-bot	httpx	94	94	0 (0.0%)	0 (0.0%)	94/94 (100.0%)